The background of the invention will be discussed in two parts.
1. Field of the Invention
This invention relates to tube or pipe bending machines, and more particularly, to a bend arm apparatus including a camming arrangement for actuation of a clamp die into engagement with a rotary bend die.
2. Description of the Prior Art
In the bending of pipes or tubes of varying size, automated pipe or tube bending machines have been developed. In such machines, the tube is fed, such as from a length of tubing or a coil, through a rotatable chuck or collect gripping arrangement, to a tube bending zone. Typically, the tube bending zone includes a rotary bend die having a concave at least partially circumferential groove corresponding to a radius of the diameter of the pipe or tube to be bent. The tube is fed until the tube is positioned at the bend die at the location to be bent. A bend arm assembly, including a clamp die mechanism is then actuated to position a clamp die, having a like formed concave groove, into abutting relation with the pipe at the bend point, and force or pressure is applied to the clamp die to physically restrain the pipe at the bend die. Rotation of the bend and clamp dies, with the pipe clamped between them, bends the pipe around the bend die. A rear portion of the pipe is restrained during bending. The pipe to be bent may be of relatively large diameter, such as an automobile or truck exhaust pipe, or may be of relatively small diameter, such as a tube for hydraulic or air pressure operated apparatus.
Prior art clamp dies for pipe or tube bending machines are shown and described in U.S. Pat. Nos. 4,178,788, and 4,063,441, both of which include clamping die arrangements for use in tube bending machines. In the latter patent, the clamp die mechanism includes a clamp die supported by a bend arm slide, which is connected for actuation by a cylinder by means of an interconnecting parallelogram and toggle linkage arrangement. A radial adjustment block is provided in alignment with the clamp die. With this arrangement, in retraction of the clamp die out of engagement with the bend die, the path of the clamp die follows an arc. In addition, with the toggle linkage actuating coupling, the amount of clamping force provided is somewhat unpredictable.
In such prior art tube bending arrangements, two problems have been encountered. One problem area relates to the clamping force of the clamp die against the tube section within the bend die. Too much force results in scoring or crimping of the pipe or tube, while too little force results in slippage of the tube during pivoting of the clamp die and bending mechanism. Either event may result in an unusable tube section. With respect to the second problem area, the clamp die mechanism has to be such that it provides very little interference with the bending operation. This is especially acute when adjacent bends in the tube are placed in close proximity resulting in a serpentine tube. If the physical dimensions of the clamp die are too large, or if the physical displacement of the clamp die during actuation is too great, it can interfere with the creation of bends in close proximity to one another.
In accordance with an aspect of the invention, it is an object of the invention to provide a new and improved bend arm assembly including a clamp die mechanism for a tube bending apparatus, in which the clamp die mechanism provides a predictable clamping force, and is actuated in such a manner to enable a minimum distance between tube bends.